Thin film el device

ABSTRACT

The present invention provides a thin film EL device having high electroluminescent efficiency, a low operating voltage, and a long lifetime. A thin film EL device of the present invention uses, as a luminescent layer, a charge-transport luminescent material that has, within a molecule, a portion contributing to charge transport and a portion contributing to luminescence where at least two molecular orbitals contributing to luminescent transition are localized.

TECHNICAL FIELD

[0001] The present invention relates to thin film EL(electroluminescent) devices and to self-luminous devices that can beused as various kinds of light sources for, for example, self-luminousflat panel displays, telecommunications, lighting, and otherapplications.

BACKGROUND ART

[0002] In recent years, LCD panels have been widely used for flat paneldisplays. However, such panels still have several drawbacks such as slowresponse time and narrow viewing angle. In addition, even in many newsystems in which these drawbacks are redressed, there still remainseveral problems, including unsatisfactory performance and increasingcosts in the manufacturing of panels. In these circumstances, thin filmEL devices are attracting attention as new light-emitting devices thathave excellent visibility because of self-luminosity, high-speedresponse, and widespread applicability. In particular, organic ELdevices, thin film EL devices that use, in all or part of the layers,organic materials, allowing for a simple film-forming step such as vapordeposition or coating at room temperature, have been the focus of muchresearch, as these devices are attractive in terms of manufacturing costas well as the above-mentioned characteristics.

[0003] In thin film EL devices (organic EL devices), the light emissionarises from the recombination of electrons and holes injected fromelectrodes. Research on such devices has long been conducted; however,since the electroluminescent efficiency of these devices was generallylow, their practical applications for light emitting devices was still along way off.

[0004] In the meantime, a device was proposed by Tang et al. in 1987 (C.W. Tang and S. A. Vanslyke, Appl. Phys. Lett., 51, 1987, pp. 913.)comprising a hole-injecting electrode (anode), a hole-transportinglayer, a luminescent layer, and an electron-injecting electrode(cathode) on a transparent substrate wherein ITO (Indium Tin Oxide) wasemployed as the anode, a 75-nm-thick layer of diamine derivative as thehole-transporting layer, a 60-nm-thick layer of aluminum quinolinecomplex as the luminescent layer, and an MgAg alloy havingelectron-injection properties and stability as the cathode. This devicenot only made improvement in the cathode but also formed a thin filmwhich had satisfactory transparency even with a film thickness of 75 nmand which was uniform and free from pinholes and the like by employing adiamine derivative, having excellent transparency, for thehole-transporting layer. Thus, because reduction in the device's totalfilm thickness became possible, light emission having high luminancewith relatively low voltages could be achieved. Specifically, with a lowvoltage of 10 V or less the device achieved a high luminance of 1000cd/m² or more and a high efficiency of 1.5 lm/W or higher. This reportled by Tang et al. spurned further investigation into improvements incathodes, suggestions on device constructions, and so forth, and thisactive investigation has continued to the present.

[0005] Thin film EL devices, generally investigated today, are outlinedbelow.

[0006] In addition to a thin film EL device, such as one described inthe above-mentioned report, having a laminate structure of an anode, ahole-transport layer, a luminescent layer, and a cathode formed on atransparent substrate, a device may comprise a hole-injecting layerformed between an anode and a hole-transport layer, may comprise anelectron-transport layer formed between a luminescent layer and acathode, or may comprise an electron-injecting layer formed between theelectron-transport layer and the cathode. Thus, by assigning functionsto each individual layer separately, it becomes possible to selectsuitable materials for each layer, resulting in improvement in devicecharacteristics.

[0007] For the transparent substrate, a glass substrate such as Corning1737 is widely used. A substrate thickness of about 0.7 mm is convenientfor use in terms of its strength and weight.

[0008] For the anode, a transparent electrode such as an ITO-sputteredfilm, an electron-beam evaporated film, or an ion-plated film is used.The film thickness is determined by the sheet resistance and visiblelight transmittance required; however, since thin film EL devices haverelatively high operating current densities, in most cases, the filmthicknesses are made to be 100 nm or more so as to reduce the sheetresistances.

[0009] For the cathode, an alloy of a low work function metal with a lowelectron injection barrier and a relatively high work function, stablemetal, such as an MgAg alloy proposed by Tang et al. or an AlLi alloy,is used.

[0010] For the layers sandwiched between the anode and the cathode, manydevices have a laminate structure, for example, of a hole-transportlayer formed to a thickness of about 80 nm by vacuum vapor deposition ofa diamine derivative (Q1-G-Q2 structure) used by Tang et al. such asN,N′-bis (3-methylphenyl)-N,N′-diphenylbenzidine (TPD) orN,N′-bis(α-naphthyl)-N,N′-diphenylbenzidine (NPD) and a luminescentlayer formed to a thickness of about 40 nm by vacuum vapor deposition ofan electron-transport luminescent material such as tris(8-quinolinolato)aluminum. In this structure, in order to increase luminance, generally,a luminescent layer is doped with a luminescent dye.

[0011] In addition, in view of the general difficulty in obtaining anorganic compound having excellent electron-transport properties such asone described above, it has also been suggested that in the luminescentlayer/electron-transport layer structure and in the hole-transportlayer/luminescent layer/electron-transport layer structure ahole-transport luminescent material be used for the luminescent layer.

[0012] For example, Japanese Unexamined Patent Publication No. 2-250292discloses a device having the hole-transport luminescentlayer/electron-transport layer structure that uses, as thehole-transport luminescent material,[4-{2-(naphthalene-1-yl)vinyl}phenyl]bis(4-methoxyphenyl)amine or[4-(2,2-diphenylvinyl)phenyl]bis(4-methoxyphenyl)amine.

[0013] International Patent Publication No. WO96/22273 discloses adevice having the hole-transport layer/hole-transport luminescentlayer/electron-transport layer structure that uses, as thehole-transport luminescent material,4,4′-bis(2,2-diphenyl-1-vinyl)-1,1′-biphenyl.

[0014] At the 1998 MRS Spring Meeting, Symposium G2.1, thehole-injecting layer/hole-transport luminescent layer/hole blockinglayer/electron-transport layer structure that uses NPD as thehole-transport luminescent material was disclosed.

[0015] Further, Japanese Unexamined Patent Publications No. 10-72580 andNo. 11-74079 also disclose various hole-transport luminescent materials.

[0016] Thus, using a hole-transport luminescent material as well as anelectron-transport luminescent material as the luminescent materialallows for the design of a wide range of materials, which in turnprovides various luminous colors. However, in terms ofelectroluminescent efficiency, lifetimes, and so forth, it cannot besaid that expectations have been met.

[0017] When devices are used in the passive-matrix line-at-a-timescanning displays, in particular, in order to attain a prescribedaverage luminance, peak luminance needs to be increased to very highlevels. This increases the operating voltage, causing the problem ofincreasing power consumption as a result of power loss or the likecaused by wiring resistance. Further, other problems arise, such as anincrease in the cost for drive circuits and a decrease in reliability.Furthermore, devices tend to have shorter lifetimes as compared to onesused under conditions of continuous light-emission.

[0018] In addition, even with devices having high electroluminescentefficiency and relatively low operating voltages at direct currentoperation, when the duty ratio increases during operation, the operatingvoltage required to attain a prescribed average luminance is rapidlyincreased and also the electroluminescent efficiency itself is reducedas the operating voltage increases.

[0019] Moreover, the above-mentioned[4-{2-(naphthalene-1-yl)vinyl}phenyl]bis(4-methoxyphenyl)amine and[4-(2,2-diphenylvinyl)phenyl]bis(4-methoxyphenyl)amine, disclosed inJapanese Unexamined Patent Publication No. 2-250292, have relativelygood hole-transport properties and high fluorescent yield. However,since both compounds are low-molecular-weight compounds, they sufferfrom the problems of low heat-resistance and particularly a shortlifetime. In addition, because the compounds require luminescent dyedoping, there is a problem concerning manufacturing.

[0020] The above-mentioned 4,4′-bis(2,2-diphenyl-1-vinyl)-1,1′-biphenyl,disclosed in International Patent Publication No. WO96/22273, issomewhat superior in terms of heat-resistance as compared to theabove-mentioned compounds. However, since the structure of the compoundis completely symmetric, the molecules easily become associated witheach other, reducing electroluminescent efficiency due to microscopiccrystallization and aggregation. Because of this, devices using thiskind of compound are unable to obtain satisfactory lifetime when usedunder conditions of continuous light-emission. In addition, since thecompound requires luminescent dye doping, there is a problem concerningmanufacturing.

[0021] For the above-mentioned Q1-G-Q2 type compound, such as onedisclosed in the 1998 MRS Spring Meeting, Symposium G2.1, besides TPDand NPD, the trimers of and the tetramers of triphenylamine have alsobeen reported. As for their heat resistance, it has been reported thatthey have sufficient levels of heat resistance. However, since thesecompounds also have high molecular symmetry, the molecules easily becomeassociated with each other, reducing electroluminescent efficiency dueto microscopic crystallization and aggregation. Because of this, herealso, devices using this kind of compound are unable to obtainsatisfactory lifetimes under continuous use. Particularly when thedevices are operated at high duty cycles, difficulties arise inachieving satisfactory electroluminescent efficiency and low operatingvoltages. In addition, since the compounds require luminescent dyedoping, there is a problem concerning manufacturing.

[0022] Devices using the above-mentioned hole-transport luminescentmaterials disclosed in Japanese Unexamined Patent Publications No.10-72580 and No. 11-74079 do not require luminescent dye doping, andthus are advantageous with regard to manufacturing. However, the deviceshave not yet achieved satisfactory electroluminescent efficiency.

DISCLOSURE OF THE INVENTION

[0023] In view of the foregoing and other problems, it is an object ofthe present invention to provide a thin film EL device that achieveshigh electroluminescent efficiency, a low operating voltage, and a longlifetime even when the device is operated with direct current or at highduty cycles.

[0024] In order to achieve the above-mentioned objects, the presentinventors designed materials having various structures and madepredictions about more specific properties of the materials by computersimulations. Thereafter, various compounds were actually synthesized andfabricated into thin film EL devices. The inventors then obtainedexperimental data on the electroluminescent characteristics andlifetimes of the devices for both direct current operation and high dutycycle operation. From an enormous amount of these experimental data, theinventors found that when some specific groups of compounds were used asthe luminescent material, the devices characteristically achievedextremely high electroluminescent efficiency, low operating voltages,and exceptionally long lifetimes over a wide range of operating dutycycles, from a direct current to 1/240.

[0025] In addition, the molecular orbitals (HOMO and LUMO) of thespecific groups of compounds were observed. The results of theobservations showed that each individual molecular orbital was localizedwithin a molecule. On the other hand, the hole transporting luminescentmaterials disclosed in Japanese Unexamined Patent Publications No.10-72580 and No. 11-74079 were found to have HOMO and LUMO, which areorbitals contributing to luminescent transition, spreading throughoutthe molecule. From these data and observations, the present inventorsfound that it is effective in improving in electroluminescent efficiencyand so forth when either a hole-transport luminescent material or anelectron-transport luminescent material (collectively referred to as“charge-transport luminescent material”) has at least two molecularorbitals contributing to luminescent transition such that the twoorbitals are localized within a molecule and overlap one another. Thus,the present invention was accomplished.

[0026] According to one aspect of the present invention there isprovided a thin film EL device comprising at least:

[0027] a hole-injecting electrode;

[0028] an electron-injecting electrode opposed to the hole-injectingelectrode; and

[0029] a luminescent layer sandwiched between the hole-injectingelectrode and the electron-injecting electrode, said luminescent layercontaining a charge-transport luminescent material having, within amolecule, a portion contributing to charge transport and a portioncontributing to luminescence where at least two molecular orbitalscontributing to luminescent transition are localized.

[0030] As with the above-mentioned structure, by using a material havinga portion contributing to luminescence where at least two molecularorbitals contributing to luminescent transition are localized, becausethe spatial overlap of the molecular orbitals contributing toluminescent transition is large, the energy of a hole-electronrecombination can be utilized more efficiently. Therefore, highelectroluminescent efficiency is achieved. Furthermore, since energyutilization efficiency is high, it is also possible to reduce theoperating voltage and extend the lifetime.

[0031] The term “portion contributing to charge transport” is hereindefined as a portion which is part of the molecular structure of thecharge-transport luminescent material and which contributes to electrontransport by hopping. One such example is a tetraphenyl phenylenediamineskeleton.

[0032] The term “portion contributing to luminescence” is herein definedas a portion which is part of the molecular structure of thecharge-transport luminescent material and which includes all molecularorbitals contributing to luminescent transition. One such example is ananthracene skeleton. It should be noted that this is the portion thatemits light.

[0033] The term “molecular orbitals contributing to luminescenttransition” is herein defined as orbitals that change the status atlight emission, and the orbitals include at least two orbitals, HOMO andLUMO. It should be noted that the molecular orbitals can be obtainedfrom a calculation in a conventional manner by using, for example,Chem3D available from CambridgeSoft Corporation, or the MOPAC 97 engineincorporated in WinMOPAC available from Fujitsu Ltd. In addition, eachorbital is defined herein to mean, based on the above calculationresults, the smallest spatial extent covering 90% or more of theprobability of existence of electrons.

[0034] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that an electron cloudof the portion contributing to charge transport and an electron cloud ofthe portion contributing to luminescence are localized such that theelectron clouds substantially do not overlap each other.

[0035] As with the above-mentioned structure, when the electron cloud ofthe portion contributing to charge transport and the electron cloud ofthe portion contributing to luminescence are localized such that theelectron clouds are substantially separated from each other, the chargetransport properties and the luminescent properties can be exhibitedindividually in different places within a molecule. In addition,quenching due to the interaction between the electron clouds can besuppressed. Consequently, a device is obtained that achieves highelectroluminescent efficiency, a low operating voltage, and an extendedlifetime.

[0036] The term “electron cloud of the portion contributing to chargetransport” is defined herein to mean the smallest spatial extentcovering 90% or more of the probability of existence of all theelectrons that are related to charge transport within a molecule.

[0037] The “electron cloud of the portion contributing to luminescence”is defined herein to mean the smallest spatial extent which spatiallyincludes at least two molecular orbitals selected from the molecularorbitals contributing to the above-mentioned luminescent transition andwhich covers 90% or more of the probability of existence of all theelectrons that are related to luminescence within a molecule.

[0038] Specifically, the term “being localized such that the electronclouds substantially do not overlap each other” herein includes the casewhere there is no overlap between electron clouds that are defined bythe spatial extent in which the probability of existence of all theelectrons is 90% but there is overlap between electron clouds in thespatial extent in which the probability of existence of all theelectrons is over 90%. As described above, the electron clouds of eachportion being localized such that the electron clouds do not overlapeach other are advantageous in exhibiting the function; it should benoted, however, that the case where electron clouds are localized suchthat the electron clouds do not overlap each other at all is notrealistic, and thus such a term is used.

[0039] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the portioncontributing to charge transport and the portion contributing toluminescence are connected by a carbon-carbon bond.

[0040] As with the above-mentioned structure, when the portioncontributing to luminescence and the portion contributing to chargetransport are connected by a carbon-carbon bond, at least two molecularorbitals contributing to luminescent transition are localized withoutspreading throughout the molecule, and the electron clouds of eachportion are localized such that the electron clouds substantially do nooverlap each other. Consequently, a device is obtained capable ofexhibiting high charge transport and luminescent properties.

[0041] The term “being connected by a carbon-carbon bond” hereinincludes not only a direct single bond between a carbon atom containedin the portion contributing to luminescence and a carbon atom containedin the portion contributing to charge transport, but also a bond througha divalent group consisting of carbon and hydrogen atoms, such as analkylene group and an arylene group. For such a divalent group, onehaving about 1 to 10 carbons is suitable. However, the “carbon-carbonbond” does not include a bond through nitrogen atoms or the like, adirect carbon-carbon double bond, and a direct carbon-carbon triple bondbecause these may hinder the localization of molecular orbitals.

[0042] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that thecharge-transport luminescent material is a compound having an asymmetricand nonplanar molecular structure.

[0043] As with the above-mentioned structure, when the molecularstructure is asymmetric and nonplanar, amorphous characteristics andnon-associating properties are exhibited, and therefore quenching due tothe interaction between each of the portions contributing toluminescence of adjacent molecules or the like can be suppressed. As aresult, a device is obtained that has high electroluminescentefficiency.

[0044] The term “asymmetric and nonplanar” is defined herein to meanthat the molecular structure at its most stable state is not symmetricwith respect to a point, a line, or a plane, but is three dimensional.

[0045] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the portioncontributing to luminescence is present within the luminescent layer at1×10²⁰ to 1×10²¹ per 1 cm³.

[0046] As with the above-mentioned structure, when the portioncontributing to luminescence is present within the luminescent layer ata specific density, a device is obtained that achieves high luminancewith high electroluminescent efficiency. This can be explained by thefact that when the density of the portion contributing to luminescenceis too low, sufficient luminance tends not to be obtained; on thecontrary, when the density is too high, quenching occurs due to theinteraction between the portions contributing to luminescence, and thuselectroluminescent efficiency tends to be degraded.

[0047] Here, the number of the portions contributing to luminescence iscounted per portion; for example, when the charge-transport luminescentmaterial has two portions contributing to luminescence within amolecule, the number of the portions contributing to luminescence perunit area equals a value that is double the number of molecules per unitarea.

[0048] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the volume ratio ofthe portion contributing to luminescence is lower than that of theportion contributing to charge transport.

[0049] As with the above-mentioned structure, when the volume ratio ofthe portion contributing to luminescence is lower than that of theportion contributing to charge transport, the possibility of quenchingdue to the interaction between the portions contributing to luminescenceis suppressed. Consequently, a device is obtained that achieves highelectroluminescent efficiency.

[0050] The term “volume ratio” is herein defined as the ratio of thevolume occupied by the portion contributing to luminescence and the liketo the total volume of a molecule having the portion contributing toluminescence and the like.

[0051] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the portioncontributing to charge transport is of a diaryl diphenyl arylenediamineskeleton.

[0052] This skeleton is particularly excellent in charge-transportproperties, and thus a thin film EL device is obtained that hasparticularly good electroluminescent efficiency and so forth. Above all,a tetraphenyl phenylenediamine skeleton, such as atetraphenyl-p-phenylenediamine skeleton and atetraphenyl-m-phenylenediamine skeleton, is suitable.

[0053] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the portioncontributing to luminescence is an aryl group containing five or moreconjugated bonds.

[0054] Such an aryl group has high luminance, and thus a thin film ELdevice is obtained that has advantages of low operating voltages and soforth. Above all, an anthracene skeleton is suitable.

[0055] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that anelectron-donating substituent is directly bonded to the portioncontributing to luminescence.

[0056] As with the above-mentioned structure, when an electron-donatingsubstituent is directly bonded to the portion contributing toluminescence, the localization of molecular orbitals contributing toluminescent transition is further increased, and thus a device isobtained that achieves higher electroluminescent efficiency.

[0057] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the charge is ahole.

[0058] According to another aspect of the present invention there isprovided

[0059] a thin film EL device comprising at least:

[0060] a hole-injecting electrode;

[0061] an electron-injecting electrode opposed to the hole-injectingelectrode; and

[0062] a luminescent layer sandwiched between the hole-injectingelectrode and the electron-injecting electrode, the luminescent layercontaining a compound represented by the following general formula (1):

[0063] where Ar1 and Ar2 may be the same or different, and eachindependently represents a substituted or unsubstituted aryl group; Ar3represents a substituted or unsubstituted arylene group; X represents asubstituent containing two or more carbon rings and non-planarly bondingto a diphenylamine portion; and Y represents a substituted orunsubstituted aryl group containing five or more conjugated bonds.

[0064] In the above-mentioned compound, the portion contributing to holetransport is of a diaryl diphenyl arylenediamine skeleton and theportion contributing to luminescence includes Y. When a compound havingsuch a molecular structure is used, a device is obtained capable ofexhibiting high hole-transport and luminescent properties. Particularly,when the portion contributing to luminescence is Y (excludingsubstituents when Y is substituted), at least two molecular orbitalscontributing to luminescent transition are localized, and an electroncloud of the portion contributing to luminescence and an electron cloudof the portion contributing to hole transport are localized such thatthe electron clouds substantially do not overlap each other, and thus asuperior device is obtained. Consequently, a device using theabove-mentioned compound as the hole-transport luminescent materialachieves high electroluminescent efficiency, a low operating voltage,and an extended lifetime.

[0065] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the compoundrepresented by the general formula (1) has a portion contributing toluminescence where at least two molecular orbitals contributing toluminescent transition are localized.

[0066] As with the above-mentioned structure, when at least twomolecular orbitals contributing to luminescent transition are localized,because the spatial overlap of the molecular orbitals is large, theefficiency of energy utilization of a hole-electron recombination isincreased. Thus, a thin film EL device is obtained that achieves highelectroluminescent efficiency.

[0067] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the X in thegeneral formula (1) is a substituent represented by the followinggeneral formula (2):

[0068] where R1 and R2 may be the same or different, and eachindependently represents a hydrogen atom or an alkyl group.

[0069] As with the above-mentioned structure, when the X in the generalformula (1) is a bulky substituent such as one represented by thegeneral formula (2), this portion becomes twisted and thus the moleculesof the hole-transport luminescent material become asymmetric andnonplanar. Thus, molecular association, crystallization, and the likeare less likely to occur, resulting in a device achieving highelectroluminescent efficiency.

[0070] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the X in thegeneral formula (1) is a substituent represented by the followinggeneral formula (3):

[0071] where R1 and R2 may be the same or different, and eachindependently represents a hydrogen atom or an alkyl group.

[0072] The substituent represented by the above-mentioned generalformula (3) is a bulky substituent in which a vinyl group is bonded to asubstituent represented by the above-mentioned formula (2). Thus,molecular association, crystallization, and the like are less likely tooccur, resulting in a device achieving high electroluminescentefficiency and so forth.

[0073] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the X in thegeneral formula (1) is a substituent represented by the followinggeneral formula (4):

[0074] where R1 and R2 may be the same or different, and eachindependently represents a hydrogen atom or an alkyl group.

[0075] The substituent represented by the above-mentioned generalformula (4) is a bulky substituent having nitrogen. Thus, hole-transportproperties can be improved and the molecules become asymmetric andnonplanar. Therefore, molecular association, crystallization, and thelike are less likely to occur, resulting in a device achieving highelectroluminescent efficiency and so forth.

[0076] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the X in thegeneral formula (1) is a substituent represented by the followinggeneral formula (5):

[0077] where R1 and R2 may be the same or different, and eachindependently represents a hydrogen atom or an alkyl group.

[0078] The substituent represented by the above-mentioned generalformula (5) is a bulky substituent having a fluorene skeleton. Thus, themolecules become asymmetric and nonplanar, and therefore molecularassociation, crystallization, and the like are less likely to occur.Consequently, a device is obtained that achieves high electroluminescentefficiency and so forth.

[0079] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the Y in thegeneral formula (1) is an aryl group substituted with anelectron-donating substituent.

[0080] As with the above-mentioned structure, when Y is substituted withan electron-donating substituent, the localization of molecular orbitalscontributing to luminescent transition is increased, resulting in adevice achieving higher electroluminescent efficiency.

[0081] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the Ar3 in thegeneral formula (1) is a p-phenylene group.

[0082] As with the above-mentioned structure, when Ar3 is a p-phenylenegroup, high electroluminescent efficiency is realized and organicsynthesis can be achieved easily, providing a cost advantage.

[0083] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the Ar3 in thegeneral formula (1) is an m-phenylene group.

[0084] As with the above-mentioned structure, when Ar3 is an m-phenylenegroup, hole-transport properties of the portion contributing to holetransport are improved, resulting in a device achieving highelectroluminescent efficiency and a low operating voltage.

[0085] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the hole-transportluminescent material is a compound represented by the following generalformula (6):

[0086] where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.

[0087] In the above-mentioned compound, the portion contributing to holetransport is of a tetraphenyl-p-phenylenediamine skeleton and theportion contributing to luminescence is an anthryl group. One phenylgroup of diphenylamine is substituted with the above-mentioned anthrylgroup and the other is substituted with a substituted or unsubstituted2,2-diphenylvinyl group. Such compound has a portion contributing toluminescence where at least two molecular orbitals contributing toluminescent transition are localized, and an electron cloud of theportion contributing to luminescence and a molecular cloud of theportion contributing to hole transport are localized such that theelectron cloud and the molecular cloud do not overlap each other.Further, since a bulky substituent, a 2,2-diphenylvinyl group, isbonded, this portion becomes twisted and thus the molecules becomeasymmetric and nonplanar. Thus, a thin film EL device is obtained thatachieves high electroluminescent efficiency, a low operating voltage,and an extended lifetime even when the device is operated at a widerange of operating conditions, from a direct current to high dutycycles.

[0088] A compound represented by the above-mentioned general formula (6)may be (4-{[4-(2,2-diphenylvinyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine,(4-{[4-(2,2-diphenylvinyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine,or the like.

[0089] In this patent specification, the names of compounds used hereinwere named so as to conform to IUPAC nomenclature rules. Specifically,the compounds were named using Chemistry 4-D Draw (available fromChemInnovation Software, Inc.) based on the structural formulae for eachcompound.

[0090] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that a compoundrepresented by the following general formula (7) is used as thehole-transport luminescent material:

[0091] where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.

[0092] The above-mentioned hole-transport luminescent material includesan anthryl group, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport, and furtherincludes a bulky substituent, a substituted or unsubstituted4,4-diphenylbuta-1,3-dienyl group. Thus, a thin film EL device isobtained that achieves particularly high electroluminescent efficiency,a low operating voltage, and an extended lifetime even when the deviceis operated at various operating conditions.

[0093] A compound represented by the above-mentioned general formula (7)may be(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine,(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine,or the like.

[0094] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the hole-transportluminescent material is a compound represented by the following generalformula (8):

[0095] where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.

[0096] The above-mentioned hole-transport luminescent material includesan anthryl group, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport, and furtherincludes a bulky substituent, a substituted or unsubstituted2-aza-2-diphenylaminovinyl group. Thus, a thin film EL device isobtained that achieves particularly high electroluminescent efficiency,a low operating voltage, and an extended lifetime even when the deviceis operated at various operating conditions.

[0097] A compound represented by the above-mentioned general formula (8)may be[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}{4-(9-anthryl)phenyl}amino)phenyl]diphenylamine,[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}{4-(10-methoxy(9-anthryl))phenyl}amino)phenyl]diphenylamine,or the like.

[0098] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the hole-transportluminescent material is a compound represented by the following generalformula (9):

[0099] where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.

[0100] The above-mentioned hole-transport luminescent material includesan anthryl group, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport, and furtherincludes a bulky substituent, a substituted or unsubstitutedfluorene-9-ylidenmethyl group. Thus, a thin film EL device is obtainedthat achieves particularly high electroluminescent efficiency, a lowoperating voltage, and an extended lifetime even when the device isoperated at various operating conditions.

[0101] A compound represented by the above-mentioned general formula (9)may be(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine,(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine,or the like.

[0102] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the hole-transportluminescent material is a compound represented by the following generalformula (10):

[0103] where R1, R2, R3, R4, R5, and R6 may be the same or different,and each independently represents a hydrogen atom, an alkyl group, or analkoxy group; and An represents an arylene group composed of two or moresubstituted or unsubstituted fused rings.

[0104] The above-mentioned hole-transport luminescent material includesan arylene group composed of two or more fused rings, corresponding tothe portion contributing to luminescence, and atetraphenyl-p-phenylenediamine skeleton, corresponding to the portioncontributing to hole transport. In addition, the material includes twobulky substituents, substituted or unsubstituted 2,2-diphenylvinylgroups. Thus, a thin film EL device is obtained that achievesparticularly high electroluminescent efficiency, a low operatingvoltage, and an extended lifetime even when the device is operated atvarious operating conditions.

[0105] A compound represented by the above-mentioned general formula(10) may be[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]diphenylamine,[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}{4-(2,2-diphenylvinyl)phenyl}amino)phenyl]bis(4-methoxyphenyl)amine,or the like.

[0106] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the hole-transportluminescent material is a compound represented by the following generalformula (11):

[0107] where R1, R2, R7, R8, R9, and R10 may be the same or different,and each independently represents a hydrogen atom, an alkyl group, or analkoxy group; and An represents an arylene group composed of two or moresubstituted or unsubstituted fused rings.

[0108] The above-mentioned hole-transport luminescent material includesan arylene group composed of two or more fused rings, corresponding tothe portion contributing to luminescence, and atetraphenyl-p-phenylenediamine skeleton, corresponding to the portioncontributing to hole transport. In addition, the material includes twobulky substituents, substituted or unsubstituted fluorene-9-ylidenmethylgroups. Thus, a thin film EL device is obtained that achievesparticularly high electroluminescent efficiency, a low operatingvoltage, and an extended lifetime even when the device is operated atvarious operating conditions.

[0109] A compound represented by the above-mentioned general formula(11) may be[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]diphenylamine,[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine,or the like.

[0110] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the hole-transportluminescent material is a compound represented by the following generalformula (12):

[0111] where R1 and R2 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and An represents an arylene group composed of two or moresubstituted or unsubstituted fused rings.

[0112] The above-mentioned hole-transport luminescent material includesan arylene group composed of two or more fused rings, corresponding tothe portion contributing to luminescence, and atetraphenyl-p-phenylenediamine skeleton, corresponding to the portioncontributing to hole transport. In addition, the hole-transportluminescent material is substituted with two bulky substituents,substituted or unsubstituted 4,4-diphenylbuta-1,3-dienyl groups. Thus, athin film EL device is obtained that achieves particularly highelectroluminescent efficiency, a low operating voltage, and an extendedlifetime even when the device is operated at various operatingconditions.

[0113] A compound represented by the above-mentioned general formula(12) may be[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]diphenylamine,[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}{4-(4,4-diphenylbuta-1,3-dienyl)phenyl}amino)phenyl]bis(4-methoxyphenyl)amine,or the like.

[0114] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the hole-transportluminescent material is a compound represented by the following generalformula (13):

[0115] where R1 and R2 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; An1 and An2 may be the same or different, and each independentlyrepresents an arylene group composed of two or more substituted orunsubstituted fused rings; and X1 and X2 may be the same or different,and each independently represents a substituted or unsubstituted2,2-diphenylvinyl group, 4,4-diphenylbuta-1,3-dienyl group, orfluorene-9-ylidenmethyl group or a hydrogen atom.

[0116] The above-mentioned hole-transport luminescent material includestwo arylene groups composed of two or more fused rings, corresponding tothe portion contributing to luminescence, and atetraphenyl-p-phenylenediamine skeleton, corresponding to the portioncontributing to hole transport. In addition, the above-mentioned arylenegroups are substituted with bulky substituents. Thus, a thin film ELdevice is obtained that achieves particularly high electroluminescentefficiency, a low operating voltage, and an extended lifetime even whenthe device is operated at various operating conditions.

[0117] A compound represented by the above-mentioned general formula(13) may be {4-[bis(4-(9-anthryl)phenyl)amino]phenyl}diphenylamine,[4-(bis{4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine,[4-(bis{4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine,[4-(bis{4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine,or the like.

[0118] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the hole-transportluminescent material is a compound represented by the following generalformula (14):

[0119] where R4 represents a hydrogen atom, an alkyl group, an alkoxygroup, or an aralkyl group; and R1, R2, and R3 may be the same ordifferent, and each independently represents a hydrogen atom, an alkylgroup, or an alkoxy group.

[0120] The above-mentioned hole-transport luminescent material includesa terphenyl group, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport. Thismaterial also includes a terphenyl group, which is the portioncontributing to luminescence, and thus a thin film EL device is obtainedthat achieves high electroluminescent efficiency, a low operatingvoltage, and an extended lifetime even when the device is operated atvarious operating conditions.

[0121] A compound represented by the above-mentioned general formula(14) may be[4-(diphenylamino)phenyl][4-(4-phenylphenyl)phenyl]phenylamine,[4-{bis(4-methoxyphenyl)amino}phenyl][4-{4-(4-methoxyphenyl)phenyl}phenyl][4-(1-methyl-1-phenylethyl)phenyl]amine,or the like.

[0122] According to another aspect of the present invention theabove-mentioned thin film EL device may be such that the hole-transportluminescent material is a compound represented by the following generalformula (15):

[0123] where R1, R2, R3, and R4 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup.

[0124] The above-mentioned hole-transport luminescent material includestwo terphenyl groups, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport. Thismaterial also includes terphenyl groups, which are the portioncontributing to luminescence, and thus a thin film EL device is obtainedthat achieves particularly high electroluminescent efficiency, a lowoperating voltage, and an extended lifetime even when the device isoperated at various operating conditions.

[0125] A compound represented by the above-mentioned general formula(15) may be[4-(diphenylamino)phenyl][bis{4-(4-phenylphenyl)phenyl}]amine,[4-{bis(4-methoxyphenyl)amino}phenyl]bis[4-{4-(4-methoxyphenyl)phenyl}phenyl]amine,or the like.

BRIEF DESCRIPTION OF THE DRAWING

[0126]FIG. 1 is a cross sectional view schematically showing thestructure of a thin film EL device according to a preferred embodimentof the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0127] Referring now to the drawing, a thin film EL device in accordancewith a preferred embodiment of the present invention will be describedbelow. FIG. 1 is a cross sectional view schematically showing thestructure of this thin film EL device.

[0128] As shown in FIG. 1, this thin film EL device comprises ahole-injecting electrode 2, an electron-injecting electrode 6 opposed tothe above-mentioned hole-injecting electrode 2, and a hole-transportlayer 3, a luminescent layer 4, and an electron-transport layer 5 thatare sandwiched between the electrodes, on a substrate 1.

[0129] For the substrate 1, there are no particular limitations as longas it is capable of supporting the hole-injecting electrode 2 and soforth, and thus any type of substrate known in the prior art can beused. It should be noted, however, that when emitted light is extractedfrom the substrate side, a transparent substrate is used. For atransparent substrate, typically, a glass substrate such as Coining 1737glass is used, but it is also possible to use a resin film such as theone made of polyester. A preferable thickness of the substrate is 0.5 to1.0 mm thickness in terms of strength and weight.

[0130] For the hole-injecting electrode 2, there are no particularlimitations as long as it functions as the anode and is capable ofinjecting holes into the hole-transport layer 3. It should be noted,however, that either the hole-injecting electrode 2 or theelectron-injecting electrode 6 described below is made to havetransparency to extract the emitted light to the outside and it is oftenthe case that normally the hole-injecting electrode 2 is made to be atransparent electrode. In this case, an ITO (indium tin oxide) film isusually used. In forming an ITO film, in order to ensure a high degreeof transparency and a low resistivity, such film-forming techniques assputtering, electron beam evaporation, or ion plating are employed. Theformed ITO film may be given various post-treatments to control itsresistivity and shape. The film thickness is determined mainly fromsheet resistance and visible light transmittance; however, since thinfilm EL devices have relatively high operating current densities, inorder to reduce the sheet resistance, films are usually formed to be athickness of 100 nm or more, generally 100 to 150 nm. In addition to anITO film, which is a transparent electrode, it is also possible to usevarious improved transparent conductive layers, such as an In₂O₃-ZnOtransparent conductive electrode (IDIXO available from Idemitsu KosanCo., Ltd.), or a coating film of a transparent conductive coating inwhich conductive powder particles are dispersed.

[0131] For the electron-injecting electrode 6, an electrode that iscomposed of an alloy of a low work function metal with a low electroninjection barrier and a relatively high work function, stable metal isused; for example, an MgAg alloy proposed by Tang et al. as described inthe Background Art or an AlLi alloy. In addition, it is possible to usevarious structures of electrodes, such as a multi-layer cathode composedof a Li thin film and an Al film, which is thicker than the Li thinfilm, or a multi-layer cathode composed of a LiF film and an Al film.

[0132] The hole-transport layer 3 and the electron-transport layer 5sandwiched between the above-mentioned hole-injecting electrode 2 andthe electron-injecting electrode 6 have no particular limitations, andthus are formed using any type of material known in the prior art. Forthe hole-transport layer 3, a layer is used composed of a materialhaving hole-transport properties, such as TPD or NPD described above. Itis also possible to use a specific material-blended type hole-transportlayer, which is disclosed in Japanese Unexamined Patent Publication No.11-260559. For the electron-transport layer 5, a layer composed ofvarious materials having electron-transport properties is used; forexample, an aluminum quinoline complex, such as the above-mentionedtris(8-quinolinolato)aluminum (Alq3), or various compounds, such as allkinds of oxadiazole derivatives or phenanthroline derivatives, can bewidely used.

[0133] Next, for the luminescent layer 4, which is the most significantfeature of the present invention, the charge-transport luminescentmaterial is used having a portion contributing to charge transport and aportion contributing to luminescence where at least two molecularorbitals (for example, HOMO and LUMO) contributing to luminescenttransition are localized. The portion contributing to charge transportmay be of, for example, a tetraphenyl phenylenediamine skeleton or thelike. With this skeleton, generally, higher electroluminescentefficiency and longer lifetimes than triphenylamine dimer (TPD and thelike), so-called Q1-G-Q2 structure, are achieved. The portioncontributing to luminescence may be of, for example, an anthraceneskeleton or the like. With this skeleton, particularly goodelectroluminescent efficiency and high charge-transport properties areachieved, and in addition low operating voltages and low powerconsumption are achieved.

[0134] Among the above-mentioned charge-transport luminescent materials,a material is particularly suitable in which an electron cloud of theportion contributing to charge transport and an electron cloud of theportion contributing to luminescence are localized such that theelectron clouds substantially do not overlap each other. When this kindof material is used, charge transport properties and luminescentproperties can be exhibited separately, and thus an excellent thin filmEL device is obtained. In addition, when a carbon atom of the portioncontributing to charge transport and a carbon atom of the portioncontributing to luminescence are connected by a carbon-carbon bond, theelectron clouds are localized individually such that the electron cloudssubstantially do not overlap each other, ensuring an excellent thin filmEL device.

[0135] The luminescent layer 4 is formed using such charge-transportluminescent materials by various film-forming techniques such as vapordeposition. Since the luminescent layer 4 of the present inventionachieves high electroluminescent efficiency, normally, it is notnecessary to dope the layer with luminescent dyes. Thus, a thin film ELdevice suitable for mass production is obtained.

[0136] A hole-transport luminescent material may be a compound that isrepresented by the above-mentioned general formula (1). Above all, acompound represented by the above-mentioned general formulae (6) to (15)is preferable, and a compound represented by the general formulae (6) to(13) is more preferable.

[0137] For substituted or unsubstituted aryl groups represented by Ar1and Ar2 in the above-mentioned formula (1), preferable examples thereofinclude the following: for an unsubstituted aryl group, one having 6 to20 carbons is suitably used. Specifically, a phenyl group, a biphenylgroup, a terphenyl group, a naphthyl group, an anthryl group, aphenanthryl group, a fluorenyl group, and the like, are suitable. Asubstituted aryl group may be one in which the above-mentionedunsubstituted aryl group is substituted with, for example, an alkylgroup having 1 to 10 carbons, an alkoxy group having 1 to 10 carbons, orthe like.

[0138] For a substituted or unsubstituted arylene group represented byAr3 in Formula (1), preferable examples thereof include the following:for an unsubstituted arylene group, one having 6 to 20 carbons issuitably used. Specifically, a phenylene group, a biphenylene group, aterphenylene group, a naphthylene group, an anthrylene group, aphenanthrylene group, a fluorenylene group, and the like, are suitable.A substituted arylene group may be one in which the above-mentionedunsubstituted arylene group is substituted with, for example, an alkylgroup having 1 to 10 carbons, an alkoxy group having 1 to 10 carbons, orthe like. Among these aryl groups, a substituted or unsubstitutedphenylene group is particularly suitable. A p-phenylene group providesan advantage which allows easy organic synthesis, and an m-phenylenegroup is advantageous because of its hole-transport properties and soforth.

[0139] For a substituent represented by X in Formula (1), one having 12to 30 carbons is suitably used. Specifically, a substituent representedby the above-mentioned formula (2) is suitable.

[0140] A substituent represented by Y in Formula (1) is a substituted orunsubstituted aryl group having five or more conjugated bonds.Preferable examples thereof include the following: for an unsubstitutedaryl group, an anthryl group or the like is suitably used. The number ofconjugated bonds is suitably about 5 to 30. For a substituted arylgroup, one in which an electron-donating substituent, such as an alkoxygroup having 1 to 10 carbons, is directly bonded to an unsubstitutedaryl group is suitable.

[0141] Further, for each alkyl group in the above-mentioned formulae,one having 1 to 10 carbons is suitably used. Specifically, a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a s-butyl group, an isobutyl group, a t-butyl group, and the likeare suitable.

[0142] For each alkoxy group in the above-mentioned formulae, one having1 to 10 carbons is suitably used. Specifically, a methoxy group, anethoxy group, a propoxy group, a butoxy group, a t-butoxy group, and thelike are suitable.

[0143] Each electron-donating substituent in the above-mentionedformulae has no particular limitations, but an alkoxy group having 1 to10 carbons, such as a methoxy group or an ethoxy group, is suitablyused.

[0144] For each arylene group formed by the condensation of two or moresubstituted or unsubstituted rings in the above-mentioned formulae,preferable examples thereof include the following: for an unsubstitutedarylene group, one having 10 to 20 carbons is suitably used.Specifically, a naphthylene group, an anthrylene group, a phenanthrylenegroup, and the like are suitable.

[0145] For each aralkyl group in the above-mentioned formulae, onehaving 7 to 20 carbons is suitably used. Specifically, a1-methyl-1-phenylethyl group and the like are suitable.

[0146] Specific examples of a hole-transport luminescent materialrepresented by the above-mentioned general formulae (6) to (15) arethose described above.

[0147] (Miscellaneous)

[0148] In the foregoing, one type of a thin film EL device was explainedhaving the hole-transport/luminescent/electron-transport layerssandwiched between the hole-injecting electrode and theelectron-injecting electrode; however, the present invention is notlimited to this specific type of the device. For example, an additionallayer, such as a hole-injecting layer, may be provided in the device, orthe hole-transport layer and/or the electron-transport layer may beomitted. For the hole-injecting layer, in order to smoothen the surfaceroughness of ITO, to attain low operating voltages by improving holeinjecting efficiency, to extend lifetimes, and so forth, it is possibleto use star-burst-amine (for example, Japanese Unexamined PatentPublication No. 3-308688), oligoamine (for example, International PatentPublication No. WO96/22273), or the like.

[0149] The present invention is explained in more detail below accordingto the specific examples. It is to be understood, however, that thepresent invention is not limited to these specific examples. It shouldbe noted that for each hole-transport luminescent material, one that issynthesized in a conventional manner and sufficiently purified was used,except where specific synthesis examples are noted.

EXAMPLE 1

[0150] First, as a substrate having a hole-injecting electrode thereon,a commercially available ITO-coated glass substrate (available fromSanyo Vacuum Industries, Co., Ltd., size: 100 mm×100 mm×t=0.7 mm, asheet resistance of about 14 Ω/□) was used, and the substrate waspatterned by photolithography such that the light-emission area is 1.4mm×1.4 mm with the overlap of the hole-injecting electrode and anelectron-injecting electrode. After the photolithography, the substratewas given a treatment as follows. The substrate was immersed in acommercially available resist stripper (a mixture of dimethyl sulfoxideand N-methyl-2-pyrrolidone) to remove the resist, then rinsed withacetone, and further immersed in fuming nitric acid for one minute tocompletely remove the resist. The ITO surfaces were cleaned bymechanically rubbing both (the top and bottom) surfaces of the substratewith a nylon brush as adequately supplying a 0.238% tetramethyl ammoniumhydroxide solution. The surfaces were then rinsed with pure water,followed by a spin dry. Thereafter, the surfaces were given oxygenplasma treatment in a commercially available plasma reactor (Model PR41,available from Yamato Scientific Co., Ltd.) for one minute at an oxygenflow rate of 20 sccm, a pressure of 0.2 Torr (1 Torr=133.322 Pa), and ahigh frequency output of 300 W.

[0151] The hole-injecting electrode-coated substrate thus prepared wasplaced in the vacuum chamber of a vacuum evaporator. The vacuumevaporator used here is one in which a main pumping system of acommercially available vacuum evaporator (Model EBV-6DA, available fromULVAC Japan, Ltd.) is modified. In this system, the main pumping systemis a turbo molecular pump with a pumping speed of 1500 liters/min(TC1500, available from Osaka Vacuum, Ltd.) and has an ultimate vacuumof about 1×10⁻⁶ Torr or less, and all vapor depositions were carried outin the range of 2 to 3×10⁻⁶ Torr. In addition, all vapor depositionswere carried out by connecting a tungsten boat for resistance-heatedevaporation to the DC power supply (PAK10-70A, available from KikusuiElectronics Corporation).

[0152] The hole-injecting electrode-coated substrate was placed in thevacuum chamber of a system such as one described above. Onto thesubstrate,N,N′-bis(4′-diphenylamino-4-biphenylyl)-N,N′-diphenylbenzidine (TPT,available from Hodogaya Chemical Co., Ltd.) and4-N,N-diphenylamino-α-phenylstilbene (PS) were co-deposited atdeposition rates of 0.3 (nm/s) and 0.01 (nm/s), respectively, to form amaterial-blended type hole-transport layer with a thickness of about 80(nm).

[0153] Then,(4-{[4-(2,2-diphenylvinyl)phenyl](4-(9-anthryl)phenyl)amino}phenyl)diphenylamine(hereafter referred to as “PPDA-PS-A”), which is a hole-transportluminescent material, was vapor deposited at a deposition rate of 0.3nm/s to form a hole-transport luminescent layer with a thickness ofabout 40 nm.

[0154] Here, the PPDA-PS-A was a compound represented by the followingchemical formula (16) and was obtained by synthesizing as follows.

[0155] As a starting material, N-acetyl-1,4-phenylenediamine (TCICatalog No. A0106, 2250 yen/25 g) was prepared and underwent the Ullmannreaction with iodobenzene. The resulting substance was then hydrolyzed,and further underwent the Ullmann reaction with 9-(4-iodophenyl)anthracene.

[0156] Thereafter, the resultant was formylated by the Vilsmeierreaction as shown in the following reaction formula (17). Here, for asolvent used for the reaction, it is possible to use DMF to obtain highreactivity, but in order to enhance reaction selectivity and increasethe proportion of the target compound, N-methylformanilide was used. Inaddition, since the Vilsmeier reaction is electrophilic addition, acarbon having the highest HOMO electron density became a reactive site,and thus the para position of the benzene ring, which is directly bondedto the nitrogen, was formylated. After the formylation, the resultantwas thoroughly isolated by column chromatography and thus the targetcompound was extracted.

[0157] Then, diethyl diphenylmethyl phosphate, obtained fromdiphenylbromomethane and ethylphosphate, was distilled under reducedpressure and used in the final reaction, and then the portion formylatedas described above was reacted with a diphenylvinyl group. A compoundthus obtained was further isolated thoroughly by column chromatography,and then further sublimed and purified sufficiently.

[0158] It should be noted that the foregoing synthesis example showsthat first, the skeleton was obtained by the Ullmann reaction, becausegenerally a vinyl bond is thought to be not resistant to hightemperature of the Ullmann reaction, and then the resultant wasformylated by the Vilsmeier reaction, and finally a diphenylvinyl groupwas added; however, it has been confirmed that a synthesis with higheryields is achieved when the coupling of an anthracene portion is carriedout rather at the end by effectively using Pd catalysts and so forth.

[0159] Next, onto the so-formed luminescent layer,tris(8-quinolinolato)aluminum (Alq3, available from DojindoLaboratories) was vapor deposited at a deposition rate of 0.3 nm/s toform an electron-transport layer with a thickness of about 20 nm.

[0160] Then, only Li from an Al—Li alloy (available from KojundoChemical Laboratory Co., Ltd., the weight ratio of Al to Li is 99:1) wasvapor deposited at low temperatures and at a deposition rate of about0.1 nm/s to form an Li layer with a thickness of about 1 nm.Subsequently, the temperature of the Al—Li alloy was further increasedand when Li was completely extracted, only Al was vapor deposited at adeposition rate of about 1.5 nm/s to form an Al layer with a thicknessof about 100 nm. Thus, a multi-layer cathode was formed.

[0161] To the thin film EL device thus fabricated, after dry nitrogenwas leaked inside the vapor deposition chamber, a Corning 7059 glass lidwas attached with an adhesive (Super Back Seal 953-7000, available fromAnelva Corporation) under a dry nitrogen atmosphere. Thus, a sample wasobtained.

[0162] A sample of a thin film EL device thus obtained was evaluated asfollows.

[0163] (Evaluation of the Device When Operated with DC Constant-current)

[0164] In order to evaluate the electroluminescent efficiency (cd/A) andthe operating voltage (V), 12 hours after the glass lid was attached tothe device, the device was operated with DC constant-current undernormal laboratory conditions with ambient temperature and humidity. Itshould be noted that the operating voltage was such a level obtained ata luminance level of 1000 (cd/m²).

[0165] As for the lifetime, under the same conditions as describedabove, a continuous light-emission test was conducted by operating thedevice at a DC constant-current level that provides an initial luminanceof 1000 (cd/m²). Then, the lifetime, which is defined as the time takenfor luminance to decrease by half (500 cd/m²), was evaluated.

[0166] Here, the device was operated with DC constant-current by using aDC constant-current power supply (Multi-Channel Current VoltageController TR6163, available from Advantest Corporation). The luminancewas measured using a luminance meter (Topcon luminescence meter BM-8,available from Topcon Corporation).

[0167] (Evaluation of the Device When Operated with PulsedConstant-current)

[0168] The electroluminescent efficiency (cd/A) and the operatingvoltage (V) were evaluated by, under the same conditions as describedabove, operating the device with pulsed constant-current. It should benoted that the operating voltage was such a level obtained at an averageluminance of 270 (cd/m²).

[0169] As for the lifetime, under the same conditions as describedabove, a continuous light-emission test was conducted by operating thedevice at a pulsed constant-current level that provides an averageluminance of 270 (cd/m²). Then, the lifetime, which is defined as thetime taken for luminance to decrease by half (135 cd/m²), was evaluated.

[0170] Here, the device was operated with pulsed constant-current byusing a pulsed constant-current drive circuit. Operating conditions weresuch that the pulse frequency was 100 Hz (10 ms), the duty ratio was1/240 (a pulse width of 42 μs), and the pulse waveform was a squarewave. Under these operating conditions, evaluations were made byoperating the device at various pulsed current levels. The luminance wasmeasured using a luminance meter (Topcon luminescence meter BM-8,available from Topcon Corporation).

[0171] In addition to the above evaluations, the quality of luminescentimages, such as uneven luminance and dark spots (non-light-emittingportions), was observed while the device was being operated to emitlight by using an optical microscope with 50 times magnification.

[0172] The results of these evaluations are provided in Table 1 to bepresented later.

EXAMPLE 2

[0173] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that(4-{[4-(2,2-diphenylvinyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine(PPDA-PS-AM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 3

[0174] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl](4-(9-anthryl)phenyl)amino}phenyl)diphenylamine(PPDA-PB-A) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 4

[0175] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(10-methoxy)(9-anthryl)]pheny}amino)phenyl)diphenylamine(PPDA-PB-AM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 5

[0176] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}(4-(9-anthryl)phenyl)amino)phenyl]diphenylamine(PPDA-PH-A) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 6

[0177] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}(4-(10-methoxy(9-anthryl))phenyl)amino)phenyl]diphenylamine(PPDA-PH-AM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 7

[0178] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine(PPDA-FM-A) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE8

[0179] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine(PPDA-FM-AM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 9

[0180] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]diphenylamine(PPDA-PS-APS) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 10

[0181] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine(M2PPDA-PS-APS) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 11

[0182] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]diphenylamine(PPDA-FM-AFM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 12

[0183] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine(M2PPDA-FM-AFM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 13

[0184] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]diphenylamine(PPDA-PB-APB) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in EXAMPLE 1. The results of theevaluations are provided in Table 1 to be presented later

EXAMPLE 14

[0185] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine(M2PPDA-PB-APB) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 15

[0186] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that{4-[bis(4-(9-anthryl)phenyl)amino]phenyl}diphenylamine (PPDA-A2) wasused for the formation of the hole-transport luminescent layer in placeof the PPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later.

EXAMPLE 16

[0187] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-(bis{4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine(PPDA-APS2) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 17

[0188] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-(bis{4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine(PPDA-APB2) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1 The results of the evaluations areprovided in Table 1 to be presented later.

EXAMPLE 18

[0189] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-(bis{4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine(PPDA-AFM2) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 19

[0190] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-(diphenylamino)phenyl][4-(4-phenylphenyl)phenyl]phenylamine (TPPDA)was used for the formation of the hole-transport luminescent layer inplace of the PPDA-PS-A. The sample was evaluated in a similar manner tothat described in Example 1. The results of the evaluations are providedin Table 1 to be presented later.

EXAMPLE 20

[0191] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-{bis(4-methoxyphenyl)amino}phenyl][4-{4-(4-methoxyphenyl)phenyl}phenyl][4-(1-methyl-1-phenylethyl)phenyl]amine(MTPPDA) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 21

[0192] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-(diphenylamino)phenyl][bis{4-(4-phenylphenyl)phenyl}]amine (T2PPDA)was used for the formation of the hole-transport luminescent layer inplace of the PPDA-PS-A. The sample was evaluated in a similar manner tothat described in Example 1. The results of the evaluations are providedin Table 1 to be presented later.

EXAMPLE 22

[0193] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-{bis(4-methoxyphenyl)amino}phenyl]bis[4-{4-(4-methoxyphenyl)phenyl}phenyl]amine(MT2PPDA) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

Comparative Example 1

[0194] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-{2-(naphthalene-1-yl)vinyl}phenyl]bis(4-methoxyphenyl)amine (DANS)was used for the formation of the hole-transport luminescent layer inplace of the PPDA-PS-A. The sample was evaluated in a similar manner tothat described in Example 1. The results of the evaluations are providedin Table 1 to be presented later.

Comparative Example 2

[0195] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-(2,2-diphenylvinyl)phenyl]bis(4-methoxyphenyl)amine (MDAPS) was usedfor the formation of the hole-transport luminescent layer in place ofthe PPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later.

Comparative Example 3

[0196] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that4,4′-bis(2,2-diphenyl-1-vinyl)-1,1′-biphenyl (DPVBi) was used for theformation of the hole-transport luminescent layer in place of thePPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later.

Comparative Example 4

[0197] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that instead of forming a40-nm-thick layer of the PPDA-PS-A, which is a hole-transportluminescent material, N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine(TPD) was vapor deposited at a deposition rate of 0.3 (nm/s) to form afilm having a thickness of 30 nm, which serves as the hole-transportluminescent layer, and then bathocuproine (BCP, available fromSigma-Aldrich Corporation) was vapor deposited at a deposition rate of0.3 (nm/s) to form a film having a thickness of 5 nm. The sample wasevaluated in a similar manner to that described in Example 1. Theresults of the evaluations are provided in Table 1 to be presentedlater.

Comparative Example 5

[0198] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that instead of forming a40-nm-thick layer of the PPDA-PS-A, which is a hole-transportluminescent material, N,N′-bis(α-naphthyl)-N,N′-diphenylbenzidine (NPD)was vapor deposited at a deposition rate of 0.3 (nm/s) to form a filmhaving a thickness of 30 nm, which serves as the hole-transportluminescent layer, and then bathocuproine (BCP, available fromSigma-Aldrich Corporation) was vapor deposited at a deposition rate of0.3 em/s) to form a film having a thickness of 5 nm. The sample wasevaluated in a similar manner to that described in Example 1. Theresults of the evaluations are provided in Table 1 to be presentedlater.

Comparative Example 6

[0199] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-(diphenylamino)phenyl]diphenylamine (TPPDA) was used for theformation of the hole-transport luminescent layer in place of thePPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later.

Comparative Example 7

[0200] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-{(4-phenylphenyl)phenylamino}phenyl](4-phenylphenyl)phenylamine(DPBBPDA) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

Comparative Example 8

[0201] A sample of the thin film EL device was fabricated in a similarmanner to that described in Example 1, except that[4-{bis(4-phenylphenyl)amino}phenyl]bis(4-phenylphenyl)amine (TBPDA) wasused for the formation of the hole-transport luminescent layer in placeof the PPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later. TABLE 1 Evaluation Result DC Constant-Pulsed Constant- Sample Current Operation Current Operation EL ELEfficiency Driving Life* Efficiency Driving Life* Example Component(cd/A) Voltage (V) (hrs) (cd/A) Voltage (V) (hrs) Others** 1 ITO/TPT +PS(80)/PPDA-PS-A(40)/Alq3(20)/Li/Al 15.4 6.1 3100 15.1 8.2 2500 Good 2ITO/TPT + PS(80)/PPDA-PS-AM(40)/Alq3(20)/Li/Al 16.7 5.9 3300 16.3 8.02600 Good 3 ITO/TPT + PS(80)/PPDA-PB-A(40)/Alq3(20)/Li/Al 15.9 5.8 290015.6 7.8 2400 Good 4 ITO/TPT + PS(80)/PPDA-PB-AM(41J)/Alq3(20)/Li/Al17.1 5.8 3000 16.7 7.7 2500 Good 5 ITO/TPT +PS(80)/PPDA-PH-A(40)/Alq3(20)/Li/Al 15.5 5.7 2800 14.9 7.8 2300 Good 6ITO/TPT + PS(80)/PPDA-PH-AM(40)/Alq3(20)/Li/Al 16.4 5.9 2900 16.0 7.92400 Good 7 ITO/TPT + PS(80)/PPDA-FM-A(40)/Alq3(20)/Li/Al 16.1 5.6 330015.7 7.7 2600 Good 8 ITO/TPT + PS(80)/PPDA-FM-AM(40)/Alq3(20)/Li/Al 17.25.5 3500 16.5 7.4 2800 Good 9 ITO/TPT +PS(80)/PPDA-PS-APS(40)/Alq3(20)/Li/Al 18.8 4.9 3300 18.3 6.9 2700 Good10 ITO/TPT + PS(80)/M2PPDA-PS-APS(40)/Alq3(20)/Li/Al 18.6 5.0 3500 18.17.0 2900 Good 11 ITO/TPT + PS(80)/PPDA-FM-AFM(40)/Alq3(20)/Li/Al 17.95.0 3600 17.2 7.2 3000 Good 12 ITO/TPT +PS(80)/M2PPDA-FM-AFM(40)/Alq3(20)/Li/Al 18.0 4.8 3700 17.2 6.7 3200 Good13 ITO/TPT + PS(80)/PPDA-PB-APB(40)/Alq3(20)/Li/Al 19.0 4.9 3200 18.06.9 2500 Good 14 ITO/TPT + PS(80)/M2PPDA-PB-APB(40)/Alq3(20)/Li/Al 19.25.1 3400 18.6 7.0 2800 Good 15 ITO/TPT +PS(80)/PPDA-A2(40)/Alq3(20)/Li/Al 17.9 5.1 3500 17.1 7.2 2900 Good 16ITO/TPT + PS(80)/PPDA-APS2(40)/Alq3(20)/Li/Al 20.2 4.9 3800 20.0 6.73300 Good 17 ITO/TPT + PS(80)/PPDA-APB2(40)/Alg3(20)/Li/Al 20.1 4.9 360019.3 6.8 3000 Good 18 ITO/TPT + PS(80)/PPDA-AFM2(40)/AIq3(20)/Li/Al 19.84.7 4000 18.9 6.6 3100 Good 19 ITO/TPT + PS(80)/TPPDA(40)/Alg3(20)/Li/Al9.1 7.1 1900 8.8 9.2 1600 Good 20 ITO/TPT +PS(80)/MTPPDA(40)/Alq3(20)/Li/Al 10.0 7.2 2200 9.7 9.2 1800 Good 21ITO/TPT + PS(80)/T2PPDA(40)/Alq3(20)/Li/Al 7.7 7.6 1600 7.5 9.4 1300Good 22 ITO/TPT + PS(80)/MT2PPDA(40)/Alq3(20)/Li/Al 8.6 7.7 1800 8.3 9.61400 Good C1 ITO/TPT + PS(80)/DANS(40)/Alq3(20)/Li/Al 1.5 9.8 170 0.913.8 90 Good C2 ITO/TFT + PS(80)/MDAPS(40)/Alq3(20)/Li/Al 1.8 9.6 1101.2 12.6 50 Good C3 ITO/TPT + PS(80)/DPVBi(40)/Alq3(20)/Li/Al 3.1 8.9300 2.3 12.3 190 Good C4 ITO/TPT + PS(80)/TPD(30)/BCP(5)/Alq3(20)/Li/Al2.1 10.2 180 1.7 15.2 80 Good C5 ITO/TPT +PS(80)/NPD(30)/BCP(5)/Alq3(20)/Li/Al 1.8 10.7 280 1.5 15.7 120 Good C6ITO/TPT + PS(80)/TPPDA(40)/Alq3(20)/Li/Al 1.7 9.7 130 1.1 13.7 70 GoodC7 ITO/TPT + PS(80)/DPBBPDA(40)/Alq3(20)/Li/Al 4.0 9.2 280 2.8 13.2 90Good C8 ITO/TPT + PS(80)/TBPDA(40)/Alq3(20)/Li/Al 3.6 9.4 350 3.2 18.4110 Good

[0202] The results in Table 1 show that according to Examples 1 to 22,the devices have high electroluminescent efficiency and achieveluminescence with good visibility with low operating voltages andself-emission. In addition, the continuous light-emission tests revealedthat the devices showed little degradation in luminance, had no defectssuch as dark spots or uneven luminance, and were capable of operatingstably over an extremely long period of time.

[0203] Particularly, even in pulsed-operation corresponding to theactual panel operation, the devices have high electroluminescentefficiency and low operating voltages. In addition, the continuouslight-emission tests revealed that the devices showed little degradationin luminance, had no defects such as dark spots or uneven luminance, andwere capable of operating stably over an extremely long period of time.

[0204] Further, the devices of Examples 1 to 18 achieve higherelectroluminescent efficiency, lower operating voltages, and longerlifetimes as compared to those of Examples 19 to 22. This may beexplained by the fact that in the devices of Example 1 to 18 theelectron clouds of the portions contributing to hole transport and theelectron clouds of the portions contributing to luminescence arelocalized such that the electron clouds substantially do not overlapeach other.

[0205] In Table 1 above, the constituent compounds of the devices ofeach example and comparative example are represented in an abbreviatedform as follows:

[0206] TPT indicatesN,N′-bis(4′-diphenylamino-4-biphenylyl)-N,N′-diphenylbenzidine;

[0207] PS indicates 4-N,N-diphenylamino-α-phenylstilbene;

[0208] The PPDA-PS-A indicates(4-{[4-(2,2-diphenylvinyl)phenyl](4-(9-anthryl)phenyl)amino}phenyl)diphenylamine;

[0209] PPDA-PS-AM indicates(4-{[4-(2,2-diphenylvinyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)dephenylamine;

[0210] PPDA-PB-A indicates(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl](4-(9-anthryl)phenyl)amino}phenyl)diphenylamine;

[0211] PPDA-PB-AM indicates(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(10-methoxy)(9-anthryl)]phenyl}amino)phenyl)diphenylamine;

[0212] PPDA-PH-A indicates[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}(4-(9-anthryl)phenyl)amino)phenyl]diphenylamine;

[0213] PPDA-PH-AM indicates[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}(4-(10-methoxy(9-anthryl))phenyl)amino)phenyl]diphenylamine;

[0214] PPDA-FM-A indicates(4-{[4-(fluorene-9-ylidenemethyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine;

[0215] PPDA-FM-AM indicates(4-{[4-(fluorene-9-ylidenemethyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine;

[0216] PPDA-PS-APS indicates[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]diphenylamine;

[0217] M2PPDA-PS-APS indicates[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine;

[0218] PPDA-FM-AFM indicates[4-({4-[10-(fluorene-9-ylidenemethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenemethyl)phenyl]amino)phenyl]diphenylamine;

[0219] M2PPDA-FM-AFM indicates[4-({4-[10-(fluorene-9-ylidenemethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenemethyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine;

[0220] PPDA-PB-APB indicates[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]-phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]diphenylamine;

[0221] M2PPDA-PB-APB indicates[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine;

[0222] PPDA-A2 indicates{4-[bis(4-(9-anthryl)phenyl)amino]phenyl}diphenylamine;

[0223] PPDA-APS2 indicates[4-(bis{4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine;

[0224] PPDA-APB2 indicates[4-(bis{4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]-phenyl}amino)phenyl]diphenylamine;

[0225] PPDA-AFM2 indicates[4-(bis{4-[10-(fluorene-9-ylidenemethyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine;

[0226] TPPDA indicates[4-(diphenylamino)phenyl][4-(4-phenylphenyl)phenyl]phenylamine;

[0227] MTPPDA indicates[4-{bis(4-mthoxyphenyl)amino}phenyl][4-{4-(4-methoxyphenyl)phenyl}phenyl][4-(1-methyl-1-phenylethyl)phenyl]amine;

[0228] T2PPDA indicates[4-(diphenylamino)phenyl][bis{4-(4-phenylphenyl)phenyl}]amine;

[0229] MT2PPDA indicates[4-{bis(4-methoxyphenyl)amino}phenyl]bis[4-{4-(4-methoxyphenyl)phenyl}phenyl]amine;

[0230] DANS indicates[4-{2-(naphthalene-1-yl)vinyl}phenyl]bis(4-methoxyphenyl)amine;

[0231] MDAPS indicates[4-(2,2-diphenylvinyl)phenyl]bis(4-methoxyphenyl)amine;

[0232] DPVBi indicates 4,4′-bis(2,2-diphenyl-1-vinyl)-1,1′-biphenyl;

[0233] TPD indicates N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine;

[0234] BCP indicates 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline(bathocuproine);

[0235] NPD indicates N,N′-bis(α-naphthyl)-N,N′-diphenylbenzidine;

[0236] TPPDA indicates [4-(diphenylamino)phenyl]diphenylamine;

[0237] DPBBPDA indicates[4-{(4-phenylphenyl)phenylamino}phenyl](4-phenylphenyl)phenylamine;

[0238] TBPDA indicates[4-{bis(4-phenylphenyl)amino}phenyl]bis(4-phenylphenyl)amine;

[0239] Alq3 indicates tris(8-quiolinolato)aluminum;

[0240] Al indicates aluminum; and

[0241] Li indicates lithium.

[0242] The laminate structures are described in sequence from the ITOelectrode side using the abbreviations with a slash (/) separating thelayers. The numbers in parentheses indicate the layer thicknesses innanometers, and the plus sign (+) indicates a layer in which twocomponents coexist such as a doped mixture.

[0243] For reference, the absorption wavelengths and oscillatorstrengths of compounds represented by the following chemical formulae(18) and (19) corresponding to a hole-transport luminescent material ofthe present invention and a compound represented by the followingchemical formula (20) that does not correspond to a hole-transportluminescent material of the present invention are provided in Table 2 tobe presented later.

TABLE 2 Absorption Wavelength (nm) Oscillator Strength Chemical Formula(18) 343.1 0.466 Chemical Formula (19) 383.3 0.836 Chemical Formula (20)376.8 0.390

[0244] Table 2 shows that the compounds represented by theabove-mentioned chemical formulae (18) and (19) have higher oscillatorstrengths than the compound represented by the chemical formula (20).The oscillator strength and the electroluminescent efficiency arecorrelated, that is to say, when the oscillator strength is high, theelectroluminescent efficiency is high. Thus, a device using the compoundrepresented by the chemical formula (18) or (19) as the luminescentmaterial achieves high electroluminescent efficiency.

[0245] In addition, the compound represented by the chemical formula(19) has higher oscillator strength than the compound represented by thechemical formula (18). The compound represented by the chemical formula(19) is one in which a methoxy group (an electron-donating substituent)is directly bonded to an anthracene skeleton (a portion contributing toluminescence) of the compound represented by the chemical formula (18).Consequently, a device using a compound, in which an electron-donatimgsubstituent is directly bonded to a portion contributing toluminescence, achieves higher electroluminescent efficiency.

Industrial Applicability

[0246] As has been described thus far, according to the presentinvention, a thin film EL device uses, as the charge-transportluminescent material, a compound represented by the above-mentionedgeneral formula (1) that has a portion contributing to charge transportand a portion contributing to luminescence where at least two molecularorbitals contributing to luminescent transition are localized. Thus, itis possible to provide self-luminous devices with excellent visibilitythat exhibit high electroluminescent efficiency, low operating voltages,and longer lifetimes even when operated at various operating voltages.In addition, the continuous light-emission tests revealed that thedevices showed little degradation in luminance and were capable ofoperating stably with low power consumption over an extremely longperiod of time.

[0247] Furthermore, even in pulsed operation corresponding to the actualoperation of the passive matrix panel, the devices have low operatingvoltages, high efficiency, and high reliability and are capable ofoperating stably with low power consumption over an extremely longperiod of time.

[0248] Thus, the present invention is useful in fields such as variouskinds of light sources used for self-luminous flat panel displays,telecommunications, lighting, and other applications.

What is claimed is:
 1. A thin film EL device comprising at least: ahole-injecting electrode; an electron-injecting electrode opposed tosaid hole-injecting electrode; and a luminescent layer sandwichedbetween said hole-injecting electrode and said electron-injectingelectrode, said luminescent layer containing a charge-transportluminescent material having, within a molecule, a portion contributingto charge transport and a portion contributing to luminescence where atleast two molecular orbitals contributing to luminescent transition arelocalized.
 2. A thin film EL device according to claim 1, wherein anelectron cloud of said portion contributing to charge transport and anelectron cloud of said portion contributing to luminescence arelocalized such that said electron clouds substantially do not overlapeach other.
 3. A thin film EL device according to claim 1, wherein saidportion contributing to charge transport and said portion contributingto luminescence are connected by a carbon-carbon bond.
 4. A thin film ELdevice according to claim 1, wherein said charge-transport luminescentmaterial is a compound having an asymmetric and nonplanar molecularstructure.
 5. A thin film EL device according to claim 1, wherein saidportion contributing to luminescence is present within said luminescentlayer at 1×10²⁰ to 1×10²¹ per 1 cm³.
 6. A thin film EL device accordingto claim 1, wherein the volume ratio of said portion contributing toluminescence is lower than that of said portion contributing to chargetransport.
 7. A thin film EL device according to claim 1, wherein saidportion contributing to charge transport is of a diaryl diphenylarylenediamine skeleton.
 8. A thin film EL device according to claim 7,wherein said diaryl diphenyl arylenediamine skeleton is a tetraphenylphenylenediamine skeleton.
 9. A thin film EL device according to claim1, wherein said portion contributing to luminescence is an aryl groupcontaining five or more conjugated bonds.
 10. A thin film EL deviceaccording to claim 9, wherein said aryl group containing five or moreconjugated bonds is of an anthracene skeleton.
 11. A thin film EL deviceaccording to claim 1, wherein an electron-donating substituent isdirectly bonded to said portion contributing to luminescence.
 12. A thinfilm EL device according to any one of claims 1-11, wherein said chargeis a hole.
 13. A thin film EL device comprising at least: ahole-injecting electrode; an electron-injecting electrode opposed tosaid hole-injecting electrode; and a luminescent layer sandwichedbetween said hole-injecting electrode and said electron-injectingelectrode, said luminescent layer containing a compound represented bythe following general formula (1):

where Ar1 and Ar2 may be the same or different, and each independentlyrepresents a substituted or unsubstituted aryl group; Ar3 represents asubstituted or unsubstituted arylene group; X represents a substituentcontaining two or more carbon rings and non-planarly bonding to adiphenylamine portion; and Y represents a substituted or unsubstitutedaryl group containing five or more conjugated bonds.
 14. A thin film ELdevice according to claim 13, wherein said compound represented by thegeneral formula (1) has a portion contributing to luminescence where atleast two molecular orbitals contributing to luminescent transition arelocalized.
 15. A thin film EL device according to claim 13, wherein saidX in the general formula (1) is a substituent represented by thefollowing general formula (2):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom or an alkyl group.
 16. A thin film EL deviceaccording to claim 13, wherein said X in the general formula (1) is asubstituent represented by the following general formula (3):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom or an alkyl group.
 17. A thin film EL deviceaccording to claim 13, wherein said X in the general formula (1) is asubstituent represented by the following general formula (4):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom or an alkyl group.
 18. A thin film EL deviceaccording to claim 13, wherein said X in the general formula (1) is asubstituent represented by the following general formula (5):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom or an alkyl group.
 19. A thin film EL deviceaccording to claim 13, wherein said Y in the general formula (1) is anaryl group substituted with an electron-donating substituent.
 20. A thinfilm EL device according to claim 13, wherein said Ar3 in the generalformula (1) is a p-phenylene group.
 21. A thin film EL device accordingto claim 13, wherein said Ar3 in the general formula (1) is anm-phenylene group.
 22. A thin film EL device according to claim 13,wherein said hole-transport luminescent material is a compoundrepresented by the following general formula (6):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.
 23. A thin film EL device according to claim 22, whereinsaid compound represented by the general formula (6) is(4-{[4-(2,2-diphenylvinyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine.24. A thin film EL device according to claim 22, wherein said compoundrepresented by the general formula (6) is(4-{[4-(2,2-diphenylvinyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine.25. A thin film EL device according to claim 13, wherein saidhole-transport luminescent material is a compound represented by thefollowing general formula (7):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.
 26. A thin film EL device according to claim 25, whereinsaid compound represented by the general formula (7) is(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine.27. A thin film EL device according to claim 25, wherein said compoundrepresented by the general formula (7) is(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine.28. A thin film EL device according to claim 13, wherein saidhole-transport luminescent material is a compound represented by thefollowing general formula (8):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.
 29. A thin film EL device according to claim 28, whereinsaid compound represented by the general formula (8) is[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}{4-(9-anthryl)phenyl}amino)phenyl]diphenylamine.30. A thin film EL device according to claim 28, wherein said compoundrepresented by the general formula (8) is[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}{4-(10-methoxy(9-anthryl))phenyl}amino)phenyl]diphenylamine.31. A thin film EL device according to claim 13, wherein saidhole-transport luminescent material is a compound represented by thefollowing general formula (9):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.
 32. A thin film EL device according to claim 31, whereinsaid compound represented by the general formula (9) is(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine.33. A thin film EL device according to claim 31, wherein said compoundrepresented by the general formula (9) is(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine.34. A thin film EL device according to claim 13, wherein saidhole-transport luminescent material is a compound represented by thefollowing general formula (10):

where R1, R2, R3, R4, R5, and R6 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and An represents an arylene group composed of two or moresubstituted or unsubstituted fused rings.
 35. A thin film EL deviceaccording to claim 34, wherein said compound represented by the generalformula (10) is[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]diphenylamine.36. A thin film EL device according to claim 34, wherein said compoundrepresented by the general formula (10) is[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}{4-(2,2-diphenylvinyl)phenyl}amino)phenyl]bis(4-methoxyphenyl)amine.37. A thin film EL device according to claim 13, wherein saidhole-transport luminescent material is a compound represented by thefollowing general formula (11):

where R1, R2, R7, R8, R9, and R10 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and An represents an arylene group composed of two or moresubstituted or unsubstituted fused rings.
 38. A thin film EL deviceaccording to claim 37, wherein said compound represented by the generalformula (11) is[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]diphenylamine.39. A thin film EL device according to claim 37, wherein said compoundrepresented by the general formula (11) is[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine.40. A thin film EL device according to claim 13, wherein saidhole-transport luminescent material is a compound represented by thefollowing general formula (12):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom, an alkyl group, or an alkoxy group; and Anrepresents an arylene group composed of two or more substituted orunsubstituted fused rings.
 41. A thin film EL device according to claim40, wherein said compound represented by the general formula (12) is[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]diphenylamine.42. A thin film EL device according to claim 40, wherein said compoundrepresented by the general formula (12) is[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}{4-(4,4-diphenylbuta-1,3-dienyl)phenyl}amino)phenyl]bis(4-methoxyphenyl)amine.43. A thin film EL device according to claim 13, wherein saidhole-transport luminescent material is a compound represented by thefollowing general formula (13):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom, an alkyl group, or an alkoxy group; An1 andAn2 may be the same or different, and each independently represents anarylene group composed of two or more substituted or unsubstituted fusedrings; and X1 and X2 may be the same or different, and eachindependently represents a substituted or unsubstituted2,2-diphenylvinyl group, 4,4-diphenylbuta-1,3-dienyl group, orfluorene-9-ylidenmethyl group or a hydrogen atom.
 44. A thin film ELdevice according to claim 43, wherein said compound represented by thegeneral formula (13) is{4-[bis(4-(9-anthryl)phenyl)amino]phenyl}diphenylamine.
 45. A thin filmEL device according to claim 43, wherein said compound represented bythe general formula (13) is[4-(bis{4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine.46. A thin film EL device according to claim 43, wherein said compoundrepresented by the general formula (13) is[4-(bis{4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine.47. A thin film EL device according to claim 43, wherein said compoundrepresented by the general formula (13) is[4-(bis{4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine.48. A thin film EL device according to claim 13, wherein saidhole-transport luminescent material is a compound represented by thefollowing general formula (14):

where R4 represents a hydrogen atom, an alkyl group, an alkoxy group, oran aralkyl group; and R1, R2, and R3 may be the same or different, andeach independently represents a hydrogen atom, an alkyl group, or analkoxy group.
 49. A thin film EL device according to claim 48, whereinsaid compound represented by the general formula (14) is[4-(diphenylamino)phenyl][4-(4-phenylphenyl)phenyl]phenylamine.
 50. Athin film EL device according to claim 48, wherein said compoundrepresented by the general formula (14) is[4-{bis(4-methoxyphenyl)amino}phenyl][4-{4-(4-methoxyphenyl)phenyl}phenyl][4-(1-methyl-1-phenylethyl)phenyl]amine.51. A thin film EL device according to claim 13, wherein saidhole-transport luminescent material is a compound represented by thefollowing general formula (15):

where R1, R2, R3, and R4 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup.
 52. A thin film EL device according to claim 51, wherein saidcompound represented by the general formula (15) is[4-(diphenylamino)phenyl][bis{4-(4-phenylphenyl)phenyl}]amine.
 53. Athin film EL device according to claim 51, wherein said compoundrepresented by the general formula (15) is[4-{bis(4-methoxyphenyl)amino}phenyl]bis[4-{4-(4-methoxyphenyl)phenyl}phenyl]amine.